The measurement of noise parameters of a linear device is of interest to users and designers of such linear devices. In this description, linear devices are considered to be devices whose output is proportional to the input of the device.
Traditionally, the measurement of noise parameters of a linear device involves generating a plurality of driving-port impedances and measuring noise powers of the device-under-test for each of the driving-port impedances. The plurality of driving-port impedances are typically generated by devices, such as impedance tuners and impedance generators.
Impedance tuners are used for a broad range of RF and microwave measurements such as load pulling for power amplifiers, testing input stability of a device, testing output stability of a device, and noise parameter measurements. Various types of impedance tuners exist such as mechanical impedance tuners and electronic impedance tuners. An example of a mechanical impedance tuner is a slide screw tuner. An example of an electronic impedance tuner is an impedance switching tuner. Tuners can be manually operated or automated.
Mechanical impedance tuners can offer advantages such as high resolution, large achievable voltage-standing-wave ratios (VSWRs), and low loss. However, mechanical impedance tuners can take time to vary impedances and do not offer greater repeatability than electronic impedance tuners. Mechanical impedance tuners can be bulky, thus, having limited portability and modularity.
Electronic impedance tuners switch between different passive structures to generate desired impedances. Electronic impedance tuners can be fast as long as their switches are not mechanical. Electronic impedance tuners offer high repeatability.
Since the measurement of noise parameters traditionally involves generating a plurality of driving-port impedances, measuring noise parameters can be time-intensive, in the order of several hours, due to the tuning of the impedance tuner to achieve the desired driving-port impedance and due to long averaging for reduced measurement uncertainty. Furthermore, inconsistencies may be introduced if the desired driving-port impedance is not repeated consistently.